Type: Email Worm

Platform: MS Windows with Internet Explorer 5.0,MS Outlook 98/2000 or MS Outlook Express

This is a worm virus spreading via Internet as infected email messages. The worm arrives as a message with no attachments - the worm uses several tricks to activate its code directly from the message body. When this message is opened, the worm code takes control, gets access to system resources (disk files and system registry), processes Outlook address book and sends infected messages to these addresses (in a similar way the Macro.Word97.Melissa"virus does).

This is the first known modern Internet worm that spreads its copies with no attached data. In case of other Internet worms a user should open the attach to activate the worm routines. In case of this worm its spreading routines take control at the moment the message itself is opened.

The Tricks

To spread its copies this worm uses two tricks. The first one is the feature of MS Outlook that allows creating messages in the HTML format. HTML messages may contain scripts that will be automatically executed at the moment the HTML message is being displayed (user opens the message). The worm uses this feature to run its code when the infected message is opened.

To spread its copies further and to bypass Internet Explorer security the worm uses another trick, the so-called "Scriptlet.Typelib" security vulnerability.

This security breach allows HTML scripts to create disk files. The worm uses this breach to create a HTA-file (HTML Applications, new type appeared with IE5) which contains the main worm code. This file is created in the Startup Windows folder, and as a result it is activated on next Windows startup. Being run as a local disk file the worm script in this HTML gets access to disk files and resources with no Internet Explorer security warning messages, connects Outlook address book and spreads itself.

Technical details

When a user opens infected message the worm script embedded into this message body is automatically activated and executed by MS Outlook. This script (by using security breach) creates the "UPDATE.HTA" file in the "C:\WINDOWS\START MENU\PROGRAMS\STARTUP" directory. The same file the worm tries to create in the "C:\WINDOWS\MENU INICIO\PROGRAMAS\INICIO\" directory (Spain Windows default name).

This "UPDATE.HTA" file contains the main worm code. It will be executed on next Windows startup because of its location in the Startup folder. The worm has a minor bug here: it supposes that Windows is always installed in the C:\WINDOWS directory, in other case the worm cannot create its file and fails to replicate further.

When the UPDATE.HTA file is executed, the worm runs Outlook application in hidden window and creates a new message to all recipients from Outlook address book in the same way as "Melissa" virus does. This new message has the HTML format and contains worms script in the body. Message subject is "BubbleBoy back!", and text body is looks like follows:

The BubbleBoy incident, pictures and sounds

http://www.towns.com/dorms/tom/bblboy.htm

(Note: the above shown web-address doesn't work)

After this message is being sent, to prevent duplicate messages sending the worm creates in system registry key:

"HKEY_LOCAL_MACHINE\Software\OUTLOOK.BubbleBoy\" = "OUTLOOK.BubbleBoy 1.0 by Zulu"

At the end the worm leaves on the screen the window with the text inside:

System error, delete "UPDATE.HTA" from the startup folder to solve this problem.

The worm also changes the Windows registration data (this routine is executed at the moment the UPDATE.HTA script takes control):

RegisteredOwner = "BubbleBoy"

RegisteredOrganization = "Vandelay Industries"

Protection

Microsoft has released an update that eliminates this security vulnerability. We strongly recommend you visit

http://support.microsoft.com/support/kb/articles/Q240/3/08.ASP and install this update.

If you do not use any HTML applications (HTA-files) at your work, there is another way to prevent infection

by viruses of this type (the worms and viruses that use "Scriptlet.Typelib" security vulnerability). It requires to remove the file

association for .HTA extension. To do this you have to follow several steps:

1. Double click the MyComputer icon on desktop.

2. In the appearing window choose menu the "View" -> "Options...". 3. On "File Types" tab in "Registered file types" listbox select

"HTML Applicaton" item.

4. Click "Remove" button and confirm action.

Close options dialog box